It is known in the art to examine the first (or sentinel) lymph node in the lymphatic system draining an area in which a cancerous growth is present. In the past, it was common to inject a non-radioactive dye into the tissue surrounding the primary tumor and then attempt to visually identify collection of the dye in the draining lymph nodes. The first lymph node visualized would be considered the sentinel lymph node. However this procedure is often non-optimal and is difficult to execute correctly. Extensive training is required and the technique has considerable difficulty with deeply located nodes, which may not be visible to the naked eye due to overlying tissue.
More recently, radionuclides have found use in guiding biopsy and surgical procedures. Radionuclides advantageously permit effective detection and treatment of disease, while minimizing harmful effects to the patient. For example, detection and treatment of malignant melanoma often involves surgical removal of the primary tumor and much of the lymphatic system draining the cutaneous tumor site. This procedure is performed to reduce the likelihood of further spread of the disease to distant areas and to identify lymph node metastases, so as to plan subsequent therapy. A similar approach has been followed in the management of breast cancer.
Radionuclides offer promise both in non-surgical survey procedures as well as in intraoperative procedures. For example, consider the task of identifying and removing only the sentinel lymph node(s) in the lymphatic system draining an area affected by tumor. A radiolabeled colloid tracer is injected subcutaneously or intradermally near the site of the primary tumor. The radioactive colloid tracer drains into the lymphatic system and becomes trapped in the first lymph node(s) in the chain of nodes. This first or sentinel node often is the first site to accumulate metastatic cancer cells. In some cases, more than one sentinel lymph node is identified.
Prior to surgery, the suspected region containing the sentinel lymph nodes is surveyed with a radiation detection probe. An appropriate probe helps localize the area of greatest radiation detection signal, which thus localizes the sentinel node position. This position is marked on the patient's skin to guide the surgeon in removing the node, or at the time of surgery, the node is identified through the skin or through a surgical incision. Alternately, the suspect area can be scanned with a gamma camera to permit identifying and marking the area of focal tracer uptake. A commonly used radiolabel is the gamma-emitter .sup.99m Tc which is typically attached to sulfur colloid.
An intraoperative radiation sensitive probe, which may be the same probe used in the initial non-surgical survey, is then used to verify node identification and especially to locate the sentinel node during surgery.
Radionuclide-guided surgery has application in fields other than sentinel node detection, for example, localizing tumors using radiolabeled antibodies or other radiopharmaceuticals such as labeled peptides, phospholipid ether analogs, and other tumor-avid tracers. Commonly used radionuclides for labelling these tracers include gamma-emitters and X-ray emitters such as .sup.99m Tc, .sup.201 Tl, .sup.111 In, .sup.123 I, and .sup.125 I, and beta-emitters such as .sup.131 I and .sup.18 F.
Several radiation sensitive probes are available commercially. U.S. Pat. No. 5,441,050 to Thurston (1995), assigned to Neoprobe Corp., discloses a solid handle whose tip includes a solid-state (CdZnTe) detector that is connected by a cable to a remote unit containing an analyzer and power source. The analyzer provides visual and audible radiation count rate information. A similar probe is also produced by Radiation Monitoring Devices. Each of these probes includes a collimator, which reduces the effects of background and scattered gamma rays.
Care Wise Medical Products Corp. produces a so-called C-Trak probe that utilizes a scintillator coupled to a photomultiplier tube to measure gamma ray flux. Capintec Inc. produces the so-called Gammed II product, which offers two probes: a CsI scintillator coupled to a silicon photodiode, or a silicon photodiode-equipped probe to detect gamma ray flux. Again, all of the probes include collimation.
Different surgical tasks and challenges require detection of different types of radiation, and detection by different sized probes. For example, when detecting radiation over relatively large areas, large-tipped probes are preferred as they exhibit greater detection sensitivity than small-tipped probes. This means that the radiation-containing focus can be identified more rapidly by the surgeon. However, the detection resolution of such probes is poor, and for more precise target resolution it is preferable to use small-tipped probes.
Unfortunately in the prior art, these goals are achieved only by replacing one probe or type of probe with another. At best, in an attempt to somewhat tailor the probe to the task at hand, some prior art probe systems offer interchangeable detector tip collimators. Unfortunately, the type of radiation to be detected by the probe remains the same, but the collimation characteristics may be user-changed. Further, the size of the probe itself is not changed, merely the collimation characteristics. A single probe unit may cost over $20,000 and requires periodic maintenance. Understandably, providing and maintaining a plurality of probes having different characteristics and/or sizes is a costly undertaking, which cost may be reflected in a higher medical bill to the patient.
What is needed is a radionuclide detecting probe whose detection characteristics and/or detector size may be readily changed. Preferably such probe should be modular in that changing the probe tip permits changing the detection characteristics and/of the detector size. Such probe should provide the user with audible and/or visual indications of relative strength of detected radiation, and should also provide for electronic enhancement of detected signal/noise. Preferably such probe should provide a wireless operation capability, to give greater freedom of movement to the practitioner using the probe. Ideally, the probe should also specifically conform to the shape of the user's hand to minimize fatigue.
The present invention provides such a probe.